Building outlines serve as data sources for various applications. However, accurately extracting outlines from scattered and irregular point clouds presents a challenge. To address this issue, a method utilizing the concept of the multi-level minimum bounding rectangle (MBR) is proposed for extracting precise outlines of regular buildings. Initially, the boundary points are segmented into groups using an iterative region growing technique. Subsequently, the group with the maximum boundary points is utilized to identify the initial MBR. The initial MBR is then decomposed into multi-level rectangles, ensuring that the boundary points align with rectangles of different levels. Ultimately, the outlines are generated using the multi-level MBR approach. To evaluate the effectiveness of the proposed method, experiments were conducted on regular buildings in Vaihingen. The results demonstrate that the proposed method achieves an accurate initial MBR with a slightly enhanced efficiency compared to the minimum area and the maximum overlapping methods. The root mean square errors of the extracted outline corners measure 0.71 m, surpassing the performance of four other comparison methods. In conclusion, the proposed method enables the effective extraction of outlines from regular buildings, providing a valuable contribution to subsequent three-dimensional reconstruction tasks.